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Old Thursday 9th March 2017, 10:34   #76
kabsetz
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Phil,

About ten years ago I decided to stop squinting and start watching with both eyes open. Rather than using an eye patch like a pirate, which has the drawback of dark-adapting the idle eye whereby going back to binoculars takes a while, I adopted the trick biathletes and some other shooters use. This is to attach an obstruction in front of the idle eye, close enough so that eye cannot focus on it but far enough that stray light prevents dark adaptation. The first one, for my Fieldscope back then, was simply made out of a bit of copper wire holding a black disk about couple of cm in front of the eye, fastened around the eyepiece base. Now, on my ATX, I have a similar thing held in place by the rubber ring that holds the eyepiece cover. They have a black surface towards the eye. Neither looked very elegant, but they work fine. Enough off-axis light enters the eye that going back to binoculars causes no difficulties whatsoever, and with the scope I can view for as long as I please with no other discomfort except some neck strain that comes from viewing down into an angled scope for more than 45 minutes.

I'm planning on making a more elegant version of this soon, and when I do, I can post some pictures. Highly recommended.

Kimmo
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Old Thursday 9th March 2017, 13:25   #77
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Nice idea Kimmo,

I've got rather attached to my eye-patch (especially since the super-glue incident ) I guess I could drill some off-axis holes in it to prevent dark adaption (must remember to take it off first though).

Seriously though it would be good to see your design when you've refined it

Phil
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Old Thursday 9th March 2017, 14:02   #78
henry link
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These Bushwacker optics covers look like they might work as "Absetz" eye obstructions. Just find a size that fits the eyepiece, flip down for transport and out for use.

http://shop.cva.com/Quake/Optic_Covers.asp
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Old Thursday 9th March 2017, 19:11   #79
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Here's an example of what an ultimate eye obstruction might look like. Perhaps I ought to get one of these and modify it to fit my Swaro. Looks a bit small for fitting around the ATX eyepiece barrel, though.

http://www.nordicmarksman.com/Ambidextrous-Blinder.html

Some contouring to match the curves of your face are beneficial, but it certainly does not need to be this complicated. My first effort was very much like the Bushwacker Henry linked, except that the disk needs to be further away from the eyepiece barrel than that hinge thingy would allow. My IPD is 66 mm, so the center of the obstruction needs to be about 66 mm to the side of the exit pupil of the EP.

If one wishes to use an eye patch, then an opaque grey patch would work better as it wouldn't cause dark adaptation. Pistol shooters especially use these. The other advantage of something fastened on the scope, though, is that there's nothing to take off of yourself before looking through your bins, nor anything to put on again.

Kimmo
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Old Thursday 9th March 2017, 19:13   #80
kabsetz
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This simple model may be easier to adapt. Cheaper too. This is very close to what I'll make next.

http://www.nordicmarksman.com/AHG-Blinder-Black.html

Kimmo
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Old Thursday 9th March 2017, 20:08   #81
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Originally Posted by kabsetz View Post
Here's an example of what an ultimate eye obstruction might look like. Perhaps I ought to get one of these and modify it to fit my Swaro. Looks a bit small for fitting around the ATX eyepiece barrel, though.

http://www.nordicmarksman.com/Ambidextrous-Blinder.html

Some contouring to match the curves of your face are beneficial, but it certainly does not need to be this complicated. My first effort was very much like the Bushwacker Henry linked, except that the disk needs to be further away from the eyepiece barrel than that hinge thingy would allow. My IPD is 66 mm, so the center of the obstruction needs to be about 66 mm to the side of the exit pupil of the EP.

If one wishes to use an eye patch, then an opaque grey patch would work better as it wouldn't cause dark adaptation. Pistol shooters especially use these. The other advantage of something fastened on the scope, though, is that there's nothing to take off of yourself before looking through your bins, nor anything to put on again.

Kimmo

Good points Kimmo, I can see the advantages of having something attached to the scope, maybe a sort of hybrid between the kind of thing Henry suggested and the ones you've linked to.

It's almost worth getting the more expensive one for the description alone - Ambidextrous Blinder - the best name for a scope accessory yet!!

P.S. Anyone want to buy a parrot?

Last edited by Torchepot : Thursday 9th March 2017 at 23:50.
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Old Thursday 9th March 2017, 22:05   #82
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Interesting. I didn't know people squinted when using spotting scopes. I just ignore my other eye and that seems to work well. (My viewing eye checks out as my dominant eye.)

Clear skies, Alan
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Old Friday 10th March 2017, 16:02   #83
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Interesting. I didn't know people squinted when using spotting scopes. I just ignore my other eye and that seems to work well. (My viewing eye checks out as my dominant eye.)

Clear skies, Alan
This is a skill that some folks find easy and others find impossible.

Lee
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Old Friday 10th March 2017, 19:55   #84
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If you want to know the equivalency of the original lens size to binoviewer size:

Example with the 95

95x95/2
Then square root
So its a 67mm binoculars
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Old Friday 10th March 2017, 21:21   #85
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Quote:
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If you want to know the equivalency of the original lens size to binoviewer size:

Example with the 95

95x95/2
Then square root
So its a 67mm binoculars
What is this based on and equivalency in what way?

Thanks, and clear skies, Alan
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Old Friday 10th March 2017, 21:36   #86
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It looks like Cosme is talking about the equivalent amount of light entering each eye, but that is a bit misleading at best.

Both eyes will get the full resolving power of the 95 mm aperture, which is important since resolving power is directly proportional to aperture. Since the incoming light beam is split, each eye will receive roughly half as many photons as with a monocular telescope. This will influence perceived brightness and contrast, but by how much and which way is hard to say (for me at least, since I have no personal experience with binoviewers) since there are also the perceptual effects coming from two optical detector units and full processor power being used instead of only half of the apparatus of the human eye-brain system.

I'm looking forward to actually testing this stuff, which I'll be able to do since I have the ATX 40-72 system already. Doing comparison viewing at various light levels with equal magnification settings should give a pretty good idea of where the binocular system works well and where it maybe works less well. My preliminary guess is that at equal magnifications, the binocular view will be superior until light levels go down somewhere between cloudy day and early twilight, but we'll see soon enough.

Kimmo
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Old Friday 10th March 2017, 21:57   #87
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Kimmo,

Thanks. There was a lot of discussion about binoviewers when they became widely available for astronomical telescopes, but I'd have to rummage around and see if I can revisit some of the discussions.

One thing was clear - the splitting of the light was at least partly compensated for by the use of two eyes, our brain's normal way of doing business.

With large telescopes, a binoviewer is a lot easier than a binoscope, although I have seen a 20-inch binocular Newtonian reflector. Fun to use under dark skies, but their time seems to have mostly passed.

Probably not in my budget, but I hope to try a BTX binoviewer someday.

Clear skies, Alan
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Old Friday 10th March 2017, 22:09   #88
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Having tried the BTX on the IWA (indoors), the only thing I can say is that I did not notice any reduction of colour/brightness. I have to admitt, I did not compare it with the ATX but I was not missing light.

A beam splitter is nothing else than two cemented diagonal prisms and logic rules that it's 50/50 in effective light but I didn't became aware of it.

Jan
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Old Friday 10th March 2017, 22:42   #89
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I normally always keep both eyes open with a telescope. Squinting degrades the image. I just ignore the other eye's image.
Second nature as an astronomer.

With rifle shooting on a range I also kept both eyes open.

However, with direct light pollution I used an eye patch at night. Changing eyes sometimes.
Or alternatively, I covered my whole head with a black cloth or even a cardboard box, keeping both eyes open.

P.S.
One of the advantages of observing from indoors is that the darker room acts as an almost complete light shield.
With the PST H alpha scope I have the curtains drawn and just the scope pointing through a gap.

Observing with Horace Dall's 110mm f/30 camera obscura is that we were in his darker very high loft and the incredible image on the white table in full colour and daylight was something I will never forget.
We saw blades of grass perhaps a mile away? We used the portable magnifier on the table if needed.
He projected a scary insect at night onto a wall in Luton over a mile away using a very high power bulb with the image going through the camera obscura that was controlled from indoors.

Last edited by Binastro : Friday 10th March 2017 at 23:02.
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Old Saturday 11th March 2017, 02:00   #90
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Quote:
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What is this based on and equivalency in what way?

Thanks, and clear skies, Alan
Hi Alan.

This a stated formula used always in cloudy nights.

You might think a binoviewer result is the lens size divided by two but susprisinly is more generous

Aside that when using two eyes the image became brighter, so at the end like the mate jan said before, you didnt get a dimmer view

I dare to say you can push the 95 btx up to 50x and still have a brighter imager (and better resolution, contrast etc) than a 80 mm at 60x in mono viewing, both with the same 1.3 exit pupil.

Last edited by Cosme : Saturday 11th March 2017 at 02:16.
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Old Saturday 11th March 2017, 10:16   #91
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If the 95mm objective would give a "true" exit pupil of (sqrt(95x95/2))/35 = 1.9mm. The binoview might compensate that with 20-40% (see link below).

http://www.cloudynights.com/topic/61...ion-summation/
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Old Saturday 11th March 2017, 13:46   #92
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Virtually all the discussion about the advantages of observing with two eyes rather than one comes from low light astronomy where the signal being detected is very close to the noise floor. I recall reading that the advantages are much reduced under bright daylight conditions where the low light 40% advantage is reduced to no more than 10%, both for brightness perception and detail retrieval. That would mean a binocular image from an aperture about 20% narrower than a monocular aperture (and set to a magnification 10% lower) would provide about the same detail and apparent brightness. If that's true, then the performance of the 95mm BTX at 35X would be the equivalent of an 80mm scope at 38.5x. The 95 ATX at 40x should be clearly superior to the BTX at 35x for apparent brightness and slightly better for detail retrieval.

Of course all of us can easily see how much advantage there is in using two eyes under daylight conditions by simply comparing the apparent brightness and detail we see through our binoculars with both eyes vs with one side covered.

Last edited by henry link : Saturday 11th March 2017 at 14:05.
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Old Saturday 11th March 2017, 13:52   #93
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Quote:
Originally Posted by Vespobuteo View Post
If the 95mm objective would give a "true" exit pupil of (sqrt(95x95/2))/35 = 1.9mm. The binoview might compensate that with 20-40% (see link below).

http://www.cloudynights.com/topic/61...ion-summation/
Thanks for the reference. That's quite a long piece!

I must admit an initial discomfort with the idea of "true exit pupil." Exit pupil is a tiny image of the illuminated objective, so it is aperture. (Stopping down the exit pupil is exactly the same as stopping down the aperture.) As magnification is increased, the exit pupil grows smaller, but it still represents the entire aperture. A beamsplitter will not change that and it seems odd to view light loss as a change in exit pupil.

I'll have to give this some thought.

Clear skies, Alan
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Old Saturday 11th March 2017, 14:33   #94
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This simple model may be easier to adapt. Cheaper too. This is very close to what I'll make next.

http://www.nordicmarksman.com/AHG-Blinder-Black.html

Kimmo
Hi Kimmo,

I ordered one of those yesterday and also bought locally a couple of Butler Creek lens covers to experiment with.

The lens covers work pretty well mounted on a Baader and a Zeiss zoom. The distance between the eyepiece lens center and the cover center when open is about 70mm, so they're wide enough to provide a blacked out view for the unused eye that completely overlaps with the telescope image seen by the eyepiece eye.

There are a few problems. One is that the Baader eyecuo rotates when zooming, so the blinder also rotates. The Zeiss eyecup works better because it doesn't rotate. Also the angle of the open lens cover is not ideal. I need to fashion some sort of stop so that it will tilt up toward the side of the head when fully open. Finally, the way I have the cover attached would not allow use with eyeglasses, as the cover has become a non adjustable eyecup.

I spent a couple of hours using the Zeiss eyepiece yesterday with no discomfort problems from squinting.

Henry

Last edited by henry link : Saturday 11th March 2017 at 14:52.
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Old Saturday 11th March 2017, 15:49   #95
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Have been using the eyepiece cover on my Swarovski for some years now to help mask light entering my non-scoping eye. It naturally falls in front of this eye when pushed to one side to 'open' the eyepiece. So I've been using my scope with both eyes open since then.

I have some sort of stigmatism in my non-scoping eye apparently, and I can easily believe it's been caused by keeping that eye closed 'unnaturally' for long periods of time while scoping. It used to take up to 30 mins for my eye to settle down after a long scoping session. I was tipped off by a birding mate and by an Anthony McGeehan publication on the possibility of using your birding scope with both eyes open.

Andy
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Old Saturday 11th March 2017, 18:14   #96
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Henry,

In your last sentence, did you mean that you squinted but had no discomfort, or that you had both eyes open with the Butler Creek lens cover and therefore didn't squint?

Andy,

I used to do the same with my Nikon Fieldscope ED 82 A, where I also turned the S.O.C:s eyepiece cover inside out so that the surface in front of my eye was black flock lining instead of green Cordura. That further improved the view. Prior to adopting the "both eyes open" philosophy, I suffered from similar problems as you report here, albeit perhaps not quite as bad.

Kimmo
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Old Saturday 11th March 2017, 20:05   #97
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Not directly pertinent to a binoviewer, but a camera obscura view in a darkened room uses both eyes, and can be utterly wonderful.
At a bird sanctuary such an instrument might be the ultimate viewing experience.

I just read the following article.

A Dollond/Wollaston telescope, which is about a rare Dollond triplet of which perhaps only 12 were made.

Dall, Hysom, Ronan.
JBAA 1980

SAO/NASA ADS

It has a lot of interesting material.
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Old Sunday 12th March 2017, 02:03   #98
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These new BTX viewers look amazing. $$$
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Old Sunday 12th March 2017, 16:07   #99
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Henry,

In your last sentence, did you mean that you squinted but had no discomfort, or that you had both eyes open with the Butler Creek lens cover and therefore didn't squint?

Kimmo
I meant that the dark cap allowed me to keep both eyes open without the distraction of a bright image from the unused eye superimposing itself over the scope field.

Like Alan and Binastro I find it easy to keep the unused eye open under dark conditions, but for me it's quite impossible if that eye is flooded with light in bright daylight.

Last edited by henry link : Sunday 12th March 2017 at 16:09.
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Old Sunday 12th March 2017, 17:21   #100
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I generally try to observe from a shaded position in daylight.
A hide, observatory or indoors would work.
For short term observing I have no problem in full daylight. Similarly with rifle shooting I had no problem keeping both eyes open and relaxed.
I trained myself to do this from age 16 or so.

Most of my observational astronomer friends keep both eyes open at night.

However, I agree that prolonged viewing in direct sunlight would be very tiring with both eyes open, as it takes effort to ignore the other eye's image for long periods.
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